Lawn mower



Nv. 28, 1939. K. A. cAsPERssoN 1 LAWN MowER Filed July l, 1938 2Sheets-Sheet l Patented Nov. 28, 1939 UNITED ES LAWN MOWER IApplicationJuly 1, 1938, Serial --N0. 217,033 In Sweden December 8, 1936 Myinvention relatesi to lawn-mowers oi the class in which movableknives-are arrangedv to circle in relation to the stationary knife forcooperation therewith.

The main-object-of the invention'is vto improve mowers of the typereferred to and to remove certain drawbacks of mowers heretofore used,In conventional-'mowers of said typeY the circling knivesare iixedtothey rotary element or elements Vby which-they are carried. Incrosssection: the plane sides-of the knives coincide or A approximatelycoincide -withthe rotation surface along which the knivesmove duringtheir circling motion When a knife xed as referred to descends from apoint on a level with the centre towards-the stationary knife the planeof the knife is successively changed from a substantiallyverticalposition to -a substantially horizontal position. As ay resultthe-knifehits the grass by its outer face due to this change of positionwhereby the grass is deflected forwardly and escapes cutting or takes aposition which is disadvantageous for the-cutting operation. Due to theimprovement eifected by my present invention this draw-back is removed.

A further object ofl my invention is to provide for a certain movementof the movable knives, in addition to the circling movement thereof inorder to obtain a more efficient cutting operation than in conventionalmowers.

The invention provides a mower of a construction in which the stationaryknife or cutter-bar is combinedwith movable knives for cooperationtherewith, and includes means to impart circling motion to themovableknives,.and` guide means to cause said movablevknives'to; rotateabouttheir longitudinal axis .simultaneously withtheir circling motion.

Theinvention further consists. in the particular construction,arrangementof parts, and cornbinations thereof hereinafter described andclaimed.

An embodiment offthe invention is shown by 45 way of example in theaccompanying drawings in which y Figures .1, 2, 3 land 4 illustrate themeans effecting the knife movement and itsvoperation diagrammatically;Figs. land 2fare-.cross-sec- 50 tional views, and Fig. Slis apartfsectional view;

Fig. 4 is a Adetail view.

Fig. 5 is -an elevation off-a lawn-mower constructed Aaccording to theinvention.

Fig. 6 is apart, crossfseQtonalvie-w ofthe ma- 55 chine illustratedinFig. 5.

Fig. 7 is a part-sectional view ofthe machine as seen from the rear.

Fig. 8 is a horizontal sectional yView offene lateral portion of the.machine.

Fig. 9 shows a knife in elevation. 5

Fig. l0 is a part-sectional view of aA modified form of guide means fortheiknives.

In the diagrammaticfFiguresl1A, the numeral I designates the shaft aboutwhich the knivesk 2 circle. Preferably, each knife has. its bar-shaped10- rear edge portion 3 journalled rotatably relatively to two .armslland-5 secured to the shaftfl and spacedapart a quarter of Varevolutionrelatively to each other. The knife2-will thus have alongitudinal inclined positionwhich -isrequired 15 for' the cuttingoperation. kFixed cna tr-unnion ii extending from the end ofthe'knifethrough the arm 4 is a bell-crank lever 'l and journalledthereon is a roller 8 which is .adapted to move in a circular groove 9in astationary. element It. 20 Thegroovei is eccentric. relative totheshaft I, the eccentricity being` equal to the radius. of.` thebell-crank lever I. The last-mentionedarrangement provides for the.guidance of the knives referred to, aswill be .described hereinafter..2.5

The position of the arm 4 marked by a in Fig. l, and. thebell-cranklever'Ltur-ntheknife 2 to a position most suitable for thecutting operation.4When the arm 4 moves'from. the position a, to the position b` in adirection .as shown bythe 30 arrow I I, theroller moves in thegroove 9and as aresult thebell-crank leverrl and the knife .secured thereto areforced to rotate in relation to the arm 4. Since the radius of thebell-crank lever and the eccentricity between the .shaft I 3 5 and the.groove 9 are equal, the bell-crank lever and the knife maintain theangular position relatively to the horizontal line shownin .thepositiona of thearm 4. In the angular position c of the Aarm i the knife'.maintains the-same po- 40 sition and .eifectsthe cutting operation byengagement with the stationary knife .I2 in such position. In theposition d of the arm. 4 and in the position-.e the knife stillmaintains zthesame angular position. rIhe plane of the.-knifethus 45maintains the position suitable for the cutting operation during theWhole revolution. 'The knivesfthus maintain a constantangularpositionrelatively to the horizontal line and have their cuttingl-edges directed rdownward or inclined downward. The ,knivesAareadvanced between the grass-stalkswiththeir edgesforemost andvhave notendency of unduly v cleflecting the grass, and no diiiioulty. isexperienced in Cutting relativelyhighgrass. After Qlliing '1.21.16zkrlYeS 55 ascend, maintaining the position referred to they will act asshovels on the grass which has been cut and throw it rearwardly forcollection in a magazine or basket arranged in the mower in aconventional manner. Consequently, the usual disadvantage that the grasswhich has been cut is carried along by the knives is prevented.

The oblique position of the knife shown in Fig. 3 is necessary asalready stated above to obtain a good shearing action against thestationary knife I2. place in such a manner that the circling knifeinitially hits the stationary knife at one end thereof, and the pointofcontact between thev knives then moves therealong successively duringthe movement. This and the fact that the knives 2 maintain their angularposition during the circling movement require an arc-shaped form of theknife edges, as shown in Fig. 3.

A particular advantage of the described ar-` rangement of the movableknives relatively to the stationary knives is that during the cuttingoperation the movable knife in its cooperation with the stationaryknife,in addition to the shearing action which is present for example in usualscissors, performs such a cutting action which occurs for example inusing a carving knife because the `edge of the movable knife moveslongitudinally relatively to the stationary knife to a certain degreeduring each revolutio-n. This feature will be clear on considering themovement of a point of the movable knife edge during one revolution, asfor instance the point a: in Fig. 3. After the knife has rotated onehalf revolution from the position shown in full lines to the positionshown in dotted lines in Fig. 3, the point .r has rotated to a positionmarked and simultaneously has moved laterally a distance y. This lateralor axial movement of the knife edge relatively to the main shaftl I isdirected toward the point of intersection between the edges of thestationary knife and themovable knife when said knives are cooperating,and as a result the movable knife tends to catch the grass between theknives and pull it into the angle therebetween. The relative movement ofthe knives as described is favourable to the cutting operation.

The mower constructed for use as shown in Figs. 5-9 corresponds in allessentials to the diagrammatic Figures 1 4, Fig. 5 illustrating anassembly of the mower construction on a reduced scale. Consequently, Idesignates the' shaft about which the knives 2 circle. The arms l5 and 5carrying the knives are shown in Figs. 7 and 8. The bell-cranksconnected to the arms d and rotatable in relation thereto are designatedby 'I and the rollers by 8. The guide groove 9 for the rollers is formedin the stationary frame I0 of the mower. The stationary knife I2 isclamped on an adjustable element in a conventional manner. The shaft Iis carried by ball bearings IB in the frame Ill as shown in Fig. 8. Oneof the ground Wheels II of the mower has formed thereon an internal gearI8 which meshes with a pinion I9 keyed to the shaft I. A ground roll 2Dof conventional type supports the rear portion of the mower. In order topermit the rear edge portion 3 of each knife 2 to be pivoted in the arms4 and 5 each knife has, at one end thereof, a trunnion 6 extendingthrough the arm 4, and at the opposite end a tapering hole 2| engaged bythe end of an adjustable set screw 22 as shown in Fig. 7. 'Ihis screwpermits theknife to be easily removed and mounted in place and also toThe cutting operation in fact takesl I set it in a position so as toprevent any undue slack and clearance during the rotation.

A construction of the groove 9 to fit exactly to the rollers 8 wouldcause considerable friction when the rollers move in the groove. Suchfriction may be avoided by constructing the guide means as in themodiiication shown in Figure l0. Ihe single roller is replaced in thisconstruction by two rollers 8a and 3b one engaging the outer wall 9a ofthe groove 9, and the other engaging the inner wall 9b thereof. It willbe noted that the walls 9a and 9b forming races for the rollers 8a and8b converge outwardly, and that the diameter of the one roller, 8b, islarger than that of the other roller, 8a. The construction permits therollers to be set in correct position for rolling against the walls ofthe groove by axial displacement of the shaft 3 of the knife such axialdisplacement being elected by means of a set screw as described withreference to the element 22 in connection with the foregoing embodiment.

The invention is not limited tothe exact construction shown in thedrawings and described with reference thereto but may be modified incomparison therewith in several respects within the scope defined by theclaims.

What I claim is:

1. In a lawn mower, a iixed cutter bar, a plurality of knives, rotatablemeans supporting said knives in circumferential spaced relations 'to bemoved successively adjacent the cutter bar, each knife beinglongitudinally rotatable with respect to said supporting means, fixedguide means, and means associated with each knife and said guide meansfor rotatingv the knives with respect to said supporting means duringrota,- tion thereof. v

2. In a lawn mower, a iixed cutter bar, a rotatable reel shaft,arms'carried by said reel shaft, a knife carried by the arms and mountedfor longitudinal rotation with respect thereto for cooperation with thecutter bar, guide means arranged eccentrically with respect to the axisof said reel shaft, and means carried by said knife engaging said guidemeans for rotating said knife longitudinally during rotation of the reelshaft.

3. In a lawn mower, a fixed cutter bar, a plurality of knives, rotatablemeans supporting said knives in circumferential spaced relations to bemoved successively adjacent the cutter bar, each knife beinglongitudinally rotatable with respect to said supporting means, fixed'circular guide means arranged eccent'rically with respect to the axisof said rotatable supporting means, and a bell crank lever carried byeach knife engaging said guide means for rotating the knives withrespect to said supporting means during rotation thereof.

4. In a lawn mower, a fixed cutterv bar, a plurality of knives,rotatable means supporting said knives in circumferential spacedrelations to be moved successively adjacent the cutter bar, each knifebeing longitudinally rotatable with respect to s'aid supporting means,fixed circular guide means arranged eccentrically with respect to theaxis of said rotatable supporting means, a bell crank lever carried byeachknife engaging said guide means for rotating the knives with respectto said supporting means during rotation thereof, and the radius of saidbell crank levers being equal to the eccentric displacement of the guidemeans with respect to theaxis of the rotatable supporting means.

5. In a lawn mower, a frame, a cutter bar alswel j iixed to the frame,rotatable means supporting said knives in circumferential spacedrelations to be moved successively adjacent the cutter bar, each knifebeing longitudinally rotatable with respect to said supporting means,said frame having a circular groove therein arranged eccentrically withrespect to the axis of said rotatable supporting means, a bell cranklever secured to each knife, and a roller carried by each bell cranklever each engaging said groove for rotating each knife with respect tosaid supporting means during rotation thereof.

6. In a lawn mower, a frame, a cutter bar fixed to the frame, rotatablemeans supporting said knives in circumferential spaced relations to bemoved successively adjacent the cutter bar, each knife beinglongitudinally rotatable with respect to said supporting means, saidframe having a circular groove therein arranged eccentrically withrespect to the axis of said rotatable supporting means, a bell cranklever secured to each knife, a roller carried by each bell crank levereach engaging said groove for rotating each knife with respect to saidsupporting means during'rotation thereof, and means for axiallyadjusting the positions of said knives and bell crank levers withrespect to saidl groove.

7. In a lawn mower, a xed cutter bar, a rotatable reel shaft,circumferentially*y spaced arms carried by said reel shaft, a knifeblade' having an arcuate shaped cutting edge carried by twocircumferentially spaced arms and mounted for longitudinal rotation withrespect thereto for cooperation with the cutter bar, guide meansarranged eccentrically with respect to the axis of said reel shaft, andmeans carried by said knife engaging said guide means for rotating saidknife longitudinally during rotation of the reel shaft, whereby thearcuate shaped cutting edge of the knife blade moves longitudinally withrespect to the xed cutter bar during yrotation of said reel shaft.

KARL ALBERT CASPERssoN.

